The present invention relates to an apparatus for transmitting power from an engine which is especially adapted for use in motor vehicles but is applicable wherever engines are to be applied to a variable load or to a load which is to be subjected to acceleration.
In many applications, such as in the operation of automobiles, a high torque must be available for starting and accelerating the vehicle from a standstill or in coping with heavy loads, while at higher velocities, a correspondingly lower torque is acceptable. Traditional automatic transmissions employ a fixed number of discrete gear ratios between the engine output and the transmission output in order to cover the range of gear ratios corresponding to a minimum velocity (or maximum gearing down) up to a maximum operating velocity. Moreover, changing from one gear ratio to another requires mechanical switching of gears. Generally, conventional automatic transmissions depend on significant slippage in a torque converter to cope with zero load velocity. Such slippage is energy wasteful and results in significant inefficiency. By being limited for practical purposes to gear ratios of about 4 to 1 or 5 to 1 in low gear, relatively large engines are required to deal with acceleration requirements from standstill. Such engine capacity is greater than that required for normal operating speeds and results in a correspondingly higher fuel consumption than would be used by an engine with smaller capacity.
One transmission designed to automatically adjust itself to the changes in torque requirements from the load is that disclosed in U.S. Pat. No. 1,203,265, granted to C. R. Radcliffe on Oct. 31, 1916, which employs a torque converter followed by a planetary gear set. The turbine output of the torque converter drives the ring gear of the planetary gear set and the engine crankshaft drives both the propeller of the torque converter and the sun gear of the planetary gear set. The driven output follower member is the planetary gear cage. In the latter device, the reaction of an increased load causes the turbine wheel to slow down with the result that by virtue of the planetary action of the gears, an increase in torque is applied to the driven member. This change in torque occurs continuously and automatically, depending only on the relative velocities of the turbine wheel and drive shaft. However, the turbine wheel in the Radcliffe device reverses its direction for a significant portion of its operation resulting in attendant heat build-up and hence energy waste. Moreover, a relatively large change in turbine wheel velocity to drive shaft velocity produces a significantly smaller relative change in output follower member velocity to turbine wheel velocity.